China's attempts to breach the online security protocol of the U.S. government hasn't ceased at all, and of specific and perennial target is the Defence establishment, a U.S. intelligence official said on Thursday.

U.S. Rear Admiral Samuel Cox told Reuters in an interview that China is constantly attempting to obtain military secrets that the Pentagon, the U.S. military headquarters, holds on its computer servers.

"(The Chinese's) level of effort against the Department of Defence is constant . . . It's continuing apace," Admiral Cox revealed.

He heads the intelligence wing of the U.S. Cyber Command, a division of Pentagon's Strategic Command, tasked to monitor and ward off intrusion tries on the computer system and networks maintained by the U.S. Defence office.

Admiral Cox, however, refused to provide further details on his claims, which again heightened suspicions that recent hacking incidents in the past few years involving high-profile attacks could be traced to foreign governments.

As a prime suspect pinpointed by U.S. intelligence reports and official reports, China has consistently denied that it has anything to do with the increasing numbers of computer attacks trained on branches of the U.S. government and its defence contractors.

In 2011, the U.S. Senate and defence firm Lockheed Martin were targeted in spates of computer system hackings that U.S. intelligence officials have mostly referred to as economic espionage workings that could only be initiated by Chinese actors.

In his speech at the Atlantic Council forum in Washington, Admiral Cox warned that "the potential for (cyber threats) to do destructive damage is very high," explaining that hackers have become more sophisticated, which also suggested that they have sufficient training and financial support.

The best answer for these serious threats, he added, is for U.S. cyber warriors to be given more teeth in fighting off foreign hackers.

Reuters said a proposal has been submitted by Admiral Cox "to elevate the cyberwarfare unit to the status of a full unified combatant command," which would effectively arm his office with greater capability to turn away ongoing and future attempts to pilfer valuable date from U.S. computer systems and networks.

The matter is expected to be decided within this year by U.S. President Barack Obama and Defence Secretary Leon Panetta, the top U.S. official added.

His revelation came as Chinese firms like Huawei Technologies and ZTE were parrying accusations that they were willing spy tools by China, making it easier for China to gather intelligence via the telecommunication equipment they sell.

Huawei, in particular, has encountered regulatory difficulties both on its U.S. and Australian operations, with Canberra prohibiting earlier this year the Chinese firm from participating in the $37-billion national broadband roll out for security reasons.

Prime Minister Julia Gillard has defended her government's decisions as in line with Australia's national interest.